The most common problem we see with freezing temperatures is the back flow preventer bonnet breaking. To stop the water flow for now, shut off the handle located on the vertical pipe (usually blue in color).
It is better to repair it after the weather gets warmer. We can repair it or replace the whole unit. You might have to go to the emergency shutoff valve to completely block water coming into your sprinkler system.
The vacuum breaker needs to be tested after the repair to ensure it is working correctly. A test report will be provided to you and your water company. Remember, only a licensed Irrigator or licensed back flow technician should do this work. Your health and safety rely on it
Replacement or repair of back flow preventer is typically an inexpensive solution versus having chemicals enter your water supply. Please have the repair work done by someone who is licensed and can test the system with a pressure differential gauge